Context. Investigations of the behavior of small-scale threads can provide an alternative approach to studying prominence dynamics and understanding its origin and nature. Aims. The behavior of threads are analyzed in a quiescent prominence, including drifting and both the horizontally and vertically oscillating motions. These indicate waves in the solar prominence. Methods. We used the Hα images at a setting wavelength of +0.076 Å. A quiescent prominence was observed by HINODE/SOT on 2008 January 15 for about 3 h in total. Results. Consistent with previous findings, prominences show numerous thread-like structures. Some threads clearly exhibit both vertically and horizontally oscillatory motions, while others are only drifting. Complicated cases show both drifting and oscillatory motions simultaneously. In the upper part of the prominence, the threads are oscillating independently of each other. We find that three threads oscillate with the same phase for at least two periods. The oscillations seem to be strongly damped since they disappear after a few periods. The maximum number of observed periods is 8 in our observations. In the lower part of the prominence, however, the different threads have a mixed character with the individual oscillatory motions unstable for one entire period. Most oscillatory motions will disappear after a half period or less, while the new oscillatory motions are excited nearby. A 5-min period is predominant, and the oscillating amplitudes show an average value of ±3.5 km s −1 . We find some upflows in the spicule layer, and they appear to transport the mass from photosphere (or spicules themselves) to the prominence. These upflows have an average velocity amplitude of 0.8 km s −1 . Conclusions. The threads exhibit three distinct behaviors. The first is only drifting, the second is typically oscillating, and the third shows both characteristics. There are no substantial differences between the periods of horizontally and vertically oscillating threads in this prominence.

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Context. Active region NOAA 10424 observed on August 5, 2003 is studied in detail by using TRACE, SOHO/MDI, BBSO Hα monograph, and GOES data. This investigation focuses on the sunspot rotation and its relation with the eruptive phenomena by analyzing the magnetic configuration that the rotation results in. Aims. It is shown that there is a close relationship between the sunspot rotation and the emerging kinked magnetic Ω-loops, where the flares occur. Methods. Through tracing the traceable features motion by using the TRACE white-light images, one can get the rotation velocities of the umbra, the penumbra, the area near the penumbra, and the area far from the penumbra. Furthermore, the evolution of the emerging kinked magnetic Ω-loops and magnetic fields were studied. Results. For the sunspot with positive polarity, the umbra, the penumbra, and the area near the penumbra exhibit a conspicuous counterclockwise rotation. Moreover, the velocities decrease from the umbra through the penumbra to the area near the penumbra. It is interesting that the rotation of the umbra, the penumbra, and the area near the penumbra are opposite to that of the area far from penumbra. The rotation velocities of the umbra, the penumbra, polarity separation, and total magnetic flux increase with time. During the largest event (M1.7/Sn flare), emerging kinked magnetic Ω-loops are observed from TRACE 171 Å images. Conclusions. The different rotation speeds of the different parts of the sunspot cause twist, and then the twist is injected through the chromosphere into the corona to trigger the flares.

To understand both the effects of dynamo and the nature of flaring activity, we identified rotating sunspots and then classified them into six types by using the data of Transition Region and Coronal Explorer and Solar and Heliospheric Observatory/Michelson Doppler Imager in Solar Cycle 23. The classification is made by their rotating directions and relative positions (leading or following sunspots), while the corresponding samples are given. The statistics of flares relevant to these sunspots are presented to show the relationship between different types of rotating sunspots and their flare productivity. It is found that some types of rotating sunspots are in favour of producing flares, and, outstandingly those active regions with sunspots of rotating direction opposite to the differential rotation have much higher strong (X-class) flare productivity. Furthermore, we found that the ratio of the number of flares defined in this paper is inconsistent to the number evolution of the six types of rotating sunspots. The maximum ratios of the six types except type VI appear after the maximum year. Additionally, there are total 60 possible patterns of rotating sunspots belonging to the six types, among which 35 patterns are found but 25 patterns remain to be discovered in other solar cycles. These results not only place further constraints on the dynamo theory but also reveal that the rotation motions of sunspots can be greatly helpful to the energy buildup of solar flares.